Enhancement of Surface Chemical and Physical Properties of Germanium–Sulfur Thin Film Using a Water‐Supplemented Carbon Dioxide Supercritical Fluid Treatment Technique

Abstract

In this study, an oxidation treatment technique suitable for the material and electronic device applications proceeding at low temperature (only 80 °C) and high pressure (3000 psi) utilizing a carbon dioxide (CO2) supercritical fluid (SCF), also known as scCO2, which is supplemented with water molecules, is reported. To demonstrate the possible effects on material and devices for the proposed SCF treatment, an amorphous germanium–sulfur (GeS) thin film and a GeS‐based resistance random access memory (RRAM) device are prepared. After the SCF treatment, electrical measurements confirm that the GeS‐based RRAM device exhibits a lower forming voltage, more stable resistance switching characteristics, and higher concentration distributions of high and low resistance states when compared to the device without SCF treatment. As for the material effects, both chemical and physical properties are examined based on material analyses results. It is concluded that the original amorphous GeS thin film transforms to a polycrystallized GeO film, confirmed by a reaction model for the SCF treatment illustrating possible oxidation and crystallization effects induced by this SCF treatment. This water‐enhanced scCO2 SCF treatment technique, thus, shows its capability as a feasible synthetic method for material modification as well as suitability for device level applications.

Topography dependence of conductivity in electrostrictive germanium sulfide nanoribbons

“…As illustrated in figure S3, ribbon-shaped GeS can be observed significantly across scanning electron microscope (SEM) images. Also, x-ray photoelectron spectroscopy (XPS) shown in figure S4 was performed to confirm surface composition, chemical state and impurity in the GeS nanoribbons, which agrees well with the XPS in the previous reports [40,41]. In addition to Ge and S elements, O, C and Au elements also can be observed in the XPS.…”

MXene-contact enhanced broadband photodetection in centimeter level GeS films

“…In addition, the binding energies of Ge (3d) at 30.4 eV, S (2p3/2) at 161.6 eV, observed by XPS in figures 2(d) and (e), agreed well with the earlier report about a-GeS films. The full survey XPS of a-GeS films can be seen in figure S1(b) [37,42]. The Ge/S atomic ratio was found to be about 1:1.04 in figure 2(f).…”

“…In addition, GeS has obvious optical absorption characteristics from the NIR to ultraviolet region, making it ideal for photoelectric devices such as high-sensitivity and broadband photodetectors [34]. Furthermore, amorphous GeS (a-GeS) can be prepared at relatively low growth temperatures and over large areas, and it has been applied into optical materials (fiber optics, advanced lasers and optical lens for transmission in the infrared band) and nonvolatile memory cells [35][36][37]. However, the integration of MXene and amorphous semiconductor that may bring about intriguing attributes has not been explored for relevant optoelectronics yet.…”

Use of a supercritical fluid treatment to improve switching region in resistive random access memory

“…2(a), are activated (denoted as the initial state). 24,25) In the reset process, the RS of a device switches from LRS to HRS when a positive bias is applied to BE. In contrast, in the set process, RS switches from HRS to LRS when a negative bias is applied to BE.…”